This invention relates to the field of blood pulse indicating devices, and is particularly concerned with the need for an easily portable, reasonably-priced, non-invasive device for sensing blood pulses and providing information concerning such vital matters as heart rate and blood pressure.
As indicated by the numerous patents in this field, there is a substantial requirement for an instrument which will measure these physiological conditions unobtrusively and accurately. In order to be easily portable and thus useful in monitoring heart reactions during active physical exertions of the patient, the instrument needs to be self-contained and self powered. The preferred, non-interfering position for mounting such an instrument is on the wrist of the patient; and its output preferably should be readable directly on the instrument.
Availability of a commercially satisfactory self-powered heart rate monitor having the attributes mentioned above would be of substantial use both in: (a) out-patient management, particularly in cases of cardiac dysfunction, and also in cases of pulmonary, systemic vascular, neural, and renal dysfunction; and (b) physical fitness training where a participant can obtain maximum benefit by functioning at an optimal heart rate level.
The following prior U.S. patents relating to this general field constitute all of the prior art known to applicant; they are the result of two novelty searches made relative to applicant's invention: U.S. Pat. Nos. Okada et al., B321,018; Norris, 3,631,849; Funfstuck et al., 3,675,643; Herczfeld et al., 3,704,706; Manuel et al., 3,742,937; Smart et al., 3,769,974; Stephens, 3,796,213; Orr et al., 3,807,388; Scheidt, 3,815,583; Raddi et al., 3,826,246; Manuel et al., 3,838,684; Page, 3,841,314; Gebben et al., 3,850,169; Dunegan, 3,871,362; Blick, 3,880,145; Wilcox, 3,881,466.
Of the listed patents, three seem to call for specific discussion herein. Smart U.S. Pat. No. 3,769,974 discloses a red light reflecting device which has "a plurality of light emitting diodes from which red light of a wavelength of from 6,000 to 9,000 angstroms is emitted." This light is reflected from an artery "to a sensor which varies as a function of variations in pulse pressure in the artery."
Herczfeld, Herczfeld and Klafter U.S. Pat. No. 3,704,706 discloses an "apparatus for detection of pulse rate . . . comprising a solid state probe . . . housed to direct light upon a patient's finger and a photodetector housed for receiving reflected light from such finger." The light source is a galium arsenide laser having a peak emission at 6,700 angstroms, in the red range of the color spectrum; and the photodetector is an NPN silicon device having high sensitivity through the frequency range of the emission spectrum of the laser.
Dunegan U.S. Pat. No. 3,871,362 discloses a pulse rate device using a phototransistor measuring device to indicate changes in reflection from the patient's finger during each heart beat.
It is applicant's opinion that the present invention provides for the first time a functionally and commercially practical solution of the general problems of pulse monitoring devices, a solution which is fundamentally different from, and radically more successful than, the prior devices in the field.